Phenotypic features of medial epiphyseal growth plate cells in the proximal tibia in Blount's disease

The aim of the study was to identify the phenotype of medial epiphyseal growth plate cells in the proximal tibia in Blount's disease. Material and methods. The study was conducted on medial epiphyseal growth plates of the proximal tibia in unilateral Blount's disease of stages III–IV. Cartilage tissue samples were obtained at the Pediatric Orthopedics Clinic of the Novosibirsk Research Institute of Traumatology and Orthopedics from 5 children (4 girls, 1 boy) aged 3 to 8 years. Growth plate cells were cultured up to passage 4 and analyzed using immunofluorescence microscopy for chondrogenic (Collagen II) and neural markers (Musashi-1, PAX6 , SOX2, NF200). Morphometric measurements were conducted with ImageJ software. Results. Two different cell phenotypes were observed in the proximal tibial growth plates of individuals with Blount's disease. Type 1: Chondrocytes exhibiting a differentiation gradient, with type II collagen positivity and absence of neural marker staining. Type 2: Cells displaying either bipolar or multipolar architecture, with multiple thin processes. Neural-phenotype cells showed positive expression of both early-stage markers (Musashi-1, PAX6, SOX2) and the mature neuronal marker NF200. The nuclear, cytoplasmic, and cellular areas, as well as nuclear-to- cytoplasmic ratios, showed statistically significant differences between the identified phenotypes. Conclusion. Neural lineage cells were detected in the dysregulated growth plate microenvironment of Blount's disease. We hypothesize that neural crest-derived cells may contribute to the pathogenesis of knee joint defects in this context.

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